Diverse fen plant communities enhance carbon-related multifunctionality, but do not mitigate negative effects of drought

International audienc

Vapor-pressure deficit and extreme climatic variables limit tree growth

Assessing the effect of global warming on forest growth requires a better understanding of species-specific responses to climate change conditions. Norway spruce and European beech are among the dominant tree species in Europe and are largely used by the timber industry. Their sensitivity to changes in climate and extreme climatic events, however, endangers their future sustainability. Identifying the key climatic factors limiting their growth and survival is therefore crucial for assessing the responses of these two species to ongoing climate change. We studied the vulnerability of beech and spruce to warmer and drier conditions by transplanting saplings from the top to the bottom of an elevational gradient in the Jura Mountains in Switzerland. We (1) demonstrated that a longer growing season due to warming could not fully account for the positive growth responses, and the positive effect on sapling productivity was species-dependent, (2) demonstrated that the contrasting growth responses of beech and spruce were mainly due to different sensitivities to elevated vapor-pressure deficits (VPD), (3) determined the species-specific limits to VPD above which growth rate began to decline, and (4) demonstrated that models incorporating extreme climatic events could account for the response of growth to warming better than models using only average values. These results support that the sustainability of forest trees in the coming decades will depend on how extreme climatic events will change, irrespective of the overall warming trend

Loss of testate amoeba functional diversity with increasing frost intensity across a continental gradient reduces microbial activity in peatlands

Soil microbial communities significantly contribute to global fluxes of nutrients and carbon. Their response to climate change, including winter warming, is expected to modify these processes through direct effects on microbial functions through osmotic stress, and changing temperature regimes. Using four European peatlands reflecting different frequencies of frost events, we show that peatland testate amoeba communities diverge among sites with different winter climates, and that this is reflected through contrasting functions. We found that exposure to harder soil frost promoted species β-diversity (species turnover) thus shifting the community composition of testate amoebae. In particular, we found that harder soil frost, and lower water-soluble phenolic compounds, induced functional turnover through the decrease of large species (-68%, > 80 μm) and the increase of small-bodied mixotrophic species (i.e. Archerella flavum; +79%). These results suggest that increased exposure to soil frost could be highly limiting for large species while smaller species are more resistant. Furthermore, we found that β-glucosidase enzymatic activity, in addition to soil temperature, strongly depended (R2 = 0.95, ANOVA) of the functional diversity of testate amoebae. Changing winter conditions can therefore strongly impact peatland decomposition process, though it remains unclear if these changes are carried–over to the growing season

Functional diversity and trait composition of vascular plant and Sphagnum moss communities during peatland succession across land uplift regions

1. Most of the carbon accumulated into peatlands is derived from Sphagnum mosses. During peatland development, the relative share of vascular plants and Sphagnum mosses in the plant community changes, which impacts ecosystem functions. Little is known on the successional development of functional plant traits or functional diversity in peatlands, although this could be a key for understanding the mechanisms behind peatland resistance to climate change. Here we aim to assess how functionality of successive plant communities change along the autogenic peatland development and the associated environmental gradients, namely peat thickness and pH, and to determine whether trait trade-offs during peatland succession are analogous between vascular plant and moss communities. 2. We collected plant community and trait data on successional peatland gradients from post-glacial rebound areas in coastal Finland, Sweden and Russia, altogether from 47 peatlands. This allowed us to analyse the changes in community-weighted mean trait values and functional diversity (diversity of traits) during peatland development. 3. Our results show comparative trait trade-offs from acquisitive species to conservative species in both vascular plant and Sphagnum moss communities during peatland development. However, mosses had higher resistance to environmental change than vascular plant communities. This was seen in the larger proportion of intraspecific trait variation than species turnover in moss traits, while the proportions were opposite for vascular plants. Similarly, the functional diversity of Sphagnum communities increased during the peatland development, while the opposite occurred for vascular plants. Most of the measured traits showed a phylogenetic signal. More so, the species common to old successional stages, namely Ericacae and Sphagna from subgroup Acutifolia were detected as most similar to their phylogenetic neighbours. 4. Synthesis. During peatland development, vegetation succession leads to the dominance of conservative plant species accustomed to high stress. At the same time, the autogenic succession and ecological engineering of Sphagna leads to higher functional diversity and intraspecific variability, which together indicate higher resistance towards environmental perturbations

Plant-microbial linkages underpin carbon sequestration in contrasting mountain tundra vegetation types

Tundra ecosystems hold large stocks of soil organic matter (SOM), likely due to low temperatures limiting rates of microbial SOM decomposition more than those of SOM accumulation from plant primary productivity and microbial necromass inputs. Here we test the hypotheses that distinct tundra vegetation types and their carbon supply to characteristic rhizosphere microbes determine SOM cycling independent of temperature. In the subarctic Scandes, we used a three-way factorial design with paired heath and meadow vegetation at each of two elevations, and with each combination of vegetation type and elevation subjected during one growing season to either ambient light (i.e., ambient plant productivity), or 95% shading (i.e., reduced plant productivity). We assessed potential above-and belowground ecosystem linkages by uni-and multivariate analyses of variance, and structural equation modelling. We observed direct coupling between tundra vegetation type and microbial community composition and function, which underpinned the ecosystem's potential for SOM storage. Greater primary productivity at low elevation and ambient light supported higher microbial biomass and nitrogen immobilisation, with lower microbial mass-specific enzymatic activity and SOM humification. Congruently, larger SOM at lower elevation and in heath sustained fungal-dominated microbial communities, which were less substrate-limited, and invested less into enzymatic SOM mineralisation, owing to a greater carbon-use efficiency (CUE). Our results highlight the importance of tundra plant community characteristics (i.e., productivity and vegetation type), via their effects on soil microbial community size, structure and physiology, as essential drivers of SOM turnover. The here documented concerted patterns in above-and belowground ecosystem functioning is strongly supportive of using plant community characteristics as surrogates for assessing tundra carbon storage potential and its evolution under climate and vegetation changes

Leaf metabolic traits reveal hidden dimensions of plant form and function

International audienceThe metabolome is the biochemical basis of plant form and function, but we know little about its macroecological variation across the plant kingdom. Here, we used the plant functional trait concept to interpret leaf metabolome variation among 457 tropical and 339 temperate plant species. Distilling metabolite chemistry into five metabolic functional traits reveals that plants vary on two major axes of leaf metabolic specialization—a leaf chemical defense spectrum and an expression of leaf longevity. Axes are similar for tropical and temperate species, with many trait combinations being viable. However, metabolic traits vary orthogonally to life-history strategies described by widely used functional traits. The metabolome thus expands the functional trait concept by providing additional axes of metabolic specialization for examining plant form and function

Leaf metabolic traits reveal hidden dimensions of plant form and function

The metabolome is the biochemical basis of plant form and function, but we know little about its macroecological variation across the plant kingdom. Here, we used the plant functional trait concept to interpret leaf metabolome variation among 457 tropical and 339 temperate plant species. Distilling metabolite chemistry into five metabolic functional traits reveals that plants vary on two major axes of leaf metabolic specialization—a leaf chemical defense spectrum and an expression of leaf longevity. Axes are similar for tropical and temperate species, with many trait combinations being viable. However, metabolic traits vary orthogonally to life-history strategies described by widely used functional traits. The metabolome thus expands the functional trait concept by providing additional axes of metabolic specialization for examining plant form and function